Ball-milled biochar (BMBC) is a typical engineering material that has promising application prospects in remediating contaminated soil and water. It is fundamental to rate the transport behaviors of BMBC in the underground environment before extensive use. In this study, the effects of the ubiquitous cations (Na+, Mg2+, and Al3+) and model organic matter (humic acid) on the transport of BMBC were investigated using laboratory column experiments. The results demonstrated the facilitated effect of HA on the transport of BMBC due to the negatively charged surface and steric effect under neutral conditions. HA and ionic strength manifested an antagonistic effect on the transport of BMBC, where the presence of one could weaken the effect from the other. We also found the charge reversal of the BMBC surface in the presence of Mg2+, thus enhancing the deposition of BMBC onto the medium surface. On the other hand, the charge reversal from Al3+-coupled acid conditions led to the restabilization and transport of BMBC in porous media. Therefore, the rational usage of BMBC is indispensable and more attention should be paid to the composition and change in underground water that might facilitate the transport of BMBC and thus lead to negative environmental implications.
The projectile engraving process of a large caliber gun is investigated by adiabatic process simulation based on smoothed particle hydrodynamics (SPH) and finite element method (FEM). The acceleration, velocity, displacement of the projectile are obtained, and the resistance force and moment applying on the projectile by the gun bore are also obtained. The resistance force varying with the travel of projectile is obtained and the curve reveal a peak in the particular position. At the beginning stage of the deformation, the force increased rapidly and then exhibits a slight transitional drop. The deformation process, equivalent stress, equivalent plastic strain, temperature and damage variable distribution of rotating band are obtained by numerical simulation. In order to visualize the simulation results, two kinds of post processing method are proposed. The frequency distribution of particles was get by particular variables, and the result showing that the maximum temperature of rotating band increment due to plastic deformation can be 150 degrees. Only few material can accumulated to the failure threshold, which indicates that large plastic deformation occurrences in rotating band while ductile fracture does no happen. The second method is to interpolate the field variable on a specified section by developing a program. The results show that the maximum equivalent stress is about 300MPa, the stress triaxility is less than zero, which indicates that most material under compression, and the maximum value of J3 related parameter is 0.5 located at rotating edge, which indicates material under shear loading, which agrees with the function of rotating band.
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